Worawongsathirat (Thai: วรวงศาธิราช) was a usurper in the Ayutthaya Kingdom, ruling for only 42 days in 1548 before being assassinated. Siamese chronicles relate that Worawongsathirat attainted the crown - his kingship is not accepted by most traditional historians.

His birth-name was "Bun Si" (or Bun Sri) (Thai: บุญศรี), and he was a Brahmin. Upon entering service to the crown as keeper of Ho Phra Thep Bidon (หอพระเทพบิดร), a cloister on the palace grounds (with duties such as organising various rites and ceremonies,) Bun Si was then styled Phan But Si Thep (พันบุตรศรีเทพ). He was later promoted to the rank of Khun and styled Khun Chinnarat (ขุนชินราช); this was perhaps even as he was having an adulterous affair with Si Suda Chan (or Sri Sudachan ศรีสุดาจันทร์), a first-class concubine of King Chairachathirat.

King Chairachathirat died in 1546, possibly poisoned by her hand. Their young son, Phra Kaewfa, ascended the throne as King Yodfa with his mother as regent.

In 1548, Yotfa was killed and Si Suda Chan, still acting as a regent, put Khun Chinnarat on the throne styled "Khun Worawongsathirat".

Those of the Suphannaphum clan responded by forming alliances with the Sukhothai clan led by Khun Phirenthorathep and Si Thammasok, and of the Nakhon Si Thammarat clan led by Khun Intharathep. Their plot to overthrow Worawongsathirat involved the discovery of a white elephant (pachyderm) in Lop Buri in 1548. White elephants are considered sacred and symbols of royal power; all those discovered are normally presented to the king. The king was told that mahouts were unable to tame the elephant, so the king was invited to go tame it, himself. On setting out by royal barge along Pla Mo Canal (Thai: คลองปลาหมอ), beside Sa Bua Canal (Thai: คลองสระบัว) Worawongsathirat was killed by gunshot. His head and that of his paramour were then displayed on spikes, and their bodies left to vultures.

Those executing the coup, Khun Piren and his fellow retired officers, gave the throne to Prince Tien, who was proclaimed Maha Chakkrapat, or "Great Emperor".